Braking for aerospace applications traditionally makes use of hydraulic piston adjusters, which may respond to input quickly. Recently, some applications for aerospace braking applications have made use of electromechanical piston actuators. These electromechanical actuators (EMA) may respond to input relatively slowly compared to their hydraulic counterparts.
Electric actuation typically does not match the response speed of hydraulic actuation. The reason for this is that in electric braking, an electric motor is used to drive through a gear train that is used to then drive a ball screw piston. The gear train serves the purpose of increasing the motor torque to obtain the high linear forces that are needed for aircraft braking. By increasing the motor's output torque through the gear train, the output actuation speed is decreased by the same ratio. For instance, the targeted actuation speed of an EMA may be selected to meet desired characteristics. However, increasing the speed output from the EMA may reduce the available torque at the output.
Reduced running clearance positions may be used to reduce the distance that an EMA actuates to apply braking force. However, a reduced running clearance position may lead to dragging brakes.